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The only approved encryption method for iOS devices at this time is the built-in whole disk encryption that is provided with iOS 4 running on a supported device, with data protection enabled. Data protection allows for applications to protect application specific data with a unique encryption key derived by from the user's passcode. Without this, application data could be accessed with a simple jailbreak. If the device originally shipped with iOS 3 (e.g. the iPhone 3GS, iPad, and iPod Touch), data protection will not be enabled until the device is restored after upgrading to iOS 4. Older devices, such as the iPhone 3G, do not support data protection or hardware encryption and as such, there is no approved encryption method for them.
To verify that data protection is enabled:
1. Tap Settings.
2. Tap General.
3. Tap Passcode Lock.
4. "Data protection is enabled" should be displayed at the bottom of the screen.
If data protection is not enabled, enable it by setting a passcode on the device:
1. Tap Settings.
2. Tap General.
3. Tap Passcode Lock.
4. Tap in a passcode.
5. Tap in the same passcode.
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